Pneumocystis carinii is a fungus that causes P. carinii pneumonia (PCP) in people with AIDS, patients undergoing cancer chemotherapy, and others with conditions causing severe immunosuppression. Although the frequency of PCP in HIV-infected persons has decreased dramatically over the fast 8 years, due first to widespread prophylaxis against PCP and more recently to the reduced immunosuppression brought on by improved anti-HIV therapy, PCP remains common in AIDS patients. A large portion of all HIV infections are in Africa yet PCP there was considered rare. However, a recent South African survey reports that PCP is the most common opportunistic infection associated with AIDS in that country—for persons of African as well as European origin (Mahomed et al., 1999, East Afr Med J. 76:80-4). An entirely new risk for PCP was identified by a study of autopsy specimens in the UK and Chile. After eliminating all cases of HIV infection, analysis of the data suggested that PCP plays a role in a significant number of cases of sudden infant death syndrome (Vargas et al., 1999, Clin Infect Dis. 29:1489-93).
Treatment for PCP is less than ideal with frequent severe side effects from the two most effective drugs, pentamidine and the combination of trimethoprim and sulfamethoxazole (cotrimoxazole, TMP-SMZ) (Wilkin, A., and Feinberg, J. (1999) Am. Fam. Physician 60, 1699-1708, 1713-1714). The mortality rate also remains high (21.5%) (Azoulay, E., Parrot, A., Flahault, A., Cesari, D., Lecomte, I., Roux, P., Saidi, F., Fartoukh, M., Bernaudin, J. F., Cadranel. J., and Mayaud, C. (1999) Am. J. Respir. Crit. Care Med. 160, 493-499).
Diagnostic methods for PCP are less than ideal. Although bronchoscopy with bronchioalveolar lavage is 95% sensitive, it is expensive, invasive and requires skilled personnel. Induced sputum, an alternative method of diagnosis, is noninvasive but is often much less sensitive (80%). Moreover, the ability to assess treatment effectiveness by means other than clinical improvement is lacking other than by the aforementioned diagnostic methods.
S-Adenosyl-L-methionine (interchangeably referred to herein as S-adenosylmethionine, AdoMet, or SAM) plays a pivotal role in the physiology of all cells, both as methyl donor in myriad of biological and biochemical events and as a precursor of polyamines. About 95% of AdoMet is used for transmethylation reactions in which the N-methyl group of the methionine moiety is transferred to large molecules such as proteins, complex lipids, and DNA or to small molecules to form lecithin, regenerate methionine, etc. (Cohen, S. (1998) A Guide to Polyamines, Oxford University Press, Oxford). The remaining 2-5% of AdoMet is decarboxylated to become the aminopropyl donor for synthesis of the essential polyamines spermidine and spermine (Newman, E. B., Budman, L. I., Chan, E. C.,
Greene, R. C., Lin. R. T., Woldringh, C. L., and D'Ari, R. (1998) J. Bacteriol. 180, 3614-3619). Transmethylation reactions result in the formation of S-adenosylhomocysteine which is then hydrolyzed by S-adenosylhomocysteine hydrolase to form adenosine and homocysteine. Decarboxylation of AdoMet is catalyzed by S-adenosylmethionine decarboxylase producing decarboxylated AdoMet, an intermediate committed to polyamine biosynthesis. Decarboxylated AdoMet donates an aminopropyl group to putrescine to form spermidine or to spermidine to form spermine. The end product of the aminopropyl transfer reactions is methylthioadenosine which is cleaved by a specific phosphorylase, the products being recycled in various ways to methionine and purines, respectively. A comprehensive review of polyamine metabolism and function has been published (Cohen, ibid.).
It is towards a facile means for both diagnosing P. carinii infection in humans and monitoring the effectiveness of treatment of the infection that the present invention is directed.
The citation of any reference herein should not be deemed as an admission that such reference is available as prior art to the instant invention.